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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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How the IPCC is more likely to underestimate the climate response

What the science says...

Select a level... Basic Intermediate

Numerous papers have documented how IPCC predictions are more likely to underestimate the climate response.

Climate Myth...

IPCC is alarmist

"Unquestionably, the U.N. Intergovernmental Panel on Climate Change (IPCC) was formed to build the scientific case for humanity being the primary cause of global warming. Such a goal is fundamentally unscientific, as it is hostile to alternative hypotheses for the causes of climate change." (Roy Spencer)

"Unquestionably, the U.N. Intergovernmental Panel on Climate Change (IPCC) was formed to build the scientific case for humanity being the primary cause of global warming. Such a goal is fundamentally unscientific, as it is hostile to alternative hypotheses for the causes of climate change."

Climate scientist Roy Spencer made this statement. He starts by suggesting something highly questionable isn’t open to being questioned. What he seeks to do is suggest, by inference, that the IPCC has an agenda, and this distorts the reports they produce. In other words, Spencer (and others) suggest that the IPCC exaggerates what the science says in favour of anthropogenic global warming. It is perfectly legitimate to question this assertion, since Spencer and others offer no evidence to support it.

Some critics go further, suggesting that the IPCC actively suppresses science that doesn’t support the theory that climate change is being caused by human activities. It is notable this ‘other science’ is rarely produced to support the accusation.

Does the IPCC accurately report the findings of science?

The IPCC was formed to report on a broad range of scientific enquiries into the climate, and our effects on it, and to summarise the science for laypeople. The science they summarise is published so it is simple to compare the primary science with the IPCC reports, and compare both to what actually took place.

There are numerous instances where the IPCC reports, which are summaries of published climate change science, have understated the case - hardly suggesting exaggeration in pursuit of an agenda. Here are some examples:

  • CO2 output from fossil fuels: observed emissions are close to the worst-case projections made by the IPCC, despite them offering a range of potential emission scenarios. (In fact, atmospheric CO2 is increasing ten times faster than any rate detected in ice core data over the last 22,000 years).
  • Sea-level rise is accelerating faster than the IPCC predicted. Actual sea-level rise is 80% higher than the median IPCC projection. By 2100 sea-level rise was predicted by the IPCC to be in the range of 18-59 cm. It is now believed that figure may be far too low, because estimates of contributions from Greenland and Antarctic ice-caps were excluded from AR4 because the data was not considered reliable. (This omission hardly supports the notion that the IPCC seeks to exaggerate global warming trends).
  • Each Arctic summer, sea-ice is melting faster than average predictions in the last IPCC report. The Arctic is experiencing a long-term loss of multi-year ice which is also accelerating.
  • The body of scientific literature has consistently shown that human greenhouse gas emissions are responsible for more global surface warming than has been observed over the past half century, whereas the IPCC only says that greenhouse gases are responsible for "most" observed warming over this timeframe.

In many similar cases, the evidence suggests that changes in climate are occurring faster, and with more intensity, than the IPCC have predicted. It is not credible to suggest the reports were biased in favour of the theory of anthropogenic global warming when the evidence demonstrates the IPCC were, in fact, so cautious.

In fact, there is evidence however to suggest that the exact opposite is actually the case, both in terms of the scientific evidence itself (see below) and the way the work of the IPCC is reported. A recent study (Freudenburg 2010) investigated what it calls 'the Asymmetry of Scientific Challenge', the phenomenon in which reports on science fail to evaluate all outcomes, favoring certain probabilities while ignoring others. They found that " scientific findings were more than twenty times as likely to support the ASC perspective [that disruption through AGW may be far worse than the IPCC has suggested] than the usual framing of the issue in the U.S. mass media".

Claims that the IPCC is alarmist are not supported by evidence, and there are clear indications that the opposite may be the case.

Basic rebuttal written by GPWayne

Update July 2015:

Here is the relevant lecture-video from Denial101x - Making Sense of Climate Science Denial

Last updated on 5 July 2015 by skeptickev. View Archives

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Comments 76 to 100 out of 138:

  1. Tom; Grey Literature is a scientific term, your own liking of grey literature or unliking is just your opinion.. The IPCC through Pachauri have repeatedly claimed their reports are only based on 'peer reviewed literature' which is a false claim - ive shown why. I dont think this is the forum to discuss why grey literature is good or bad or what makes its referencing it dangerous - this is a topic well versed in scientific circles when producing scientific papers etc.
  2. krisbaum @76, "grey literature" is a term from library and information science and refers to the accessibility of the literature, not its quality, nor even the quality of the review process it undergoes. There are many examples of grey literature that undergo far more rigorous review than the normal peer reviewed literature - IPCC reports being just one example. Consequently your blanket condemnation of grey literature is misinformed. It is also evasive. Your attack on the IPCC's integrity is based on the fact that the IPCC uses grey literature, and indeed it says it does. That is a matter of complete irrelevance unless you can also show that the grey literature actually used by the IPCC is actually of dubious quality. To mount the argument that IPCC reports are dubious because they used grey literature, but then to insist that the dubious nature of grey literature be treated as an axiom is to beg the entire question. Here is the challenge you need to take - go through the 54 purported examples of grey literature in the IPCC AR4 WG1 Chapt 1 as identified by P Gosselin, and show: 1) Why the reference should be considered of low quality such that it should not be used in the report; 2) Why the use made of the reference in the report was inappropriate given its nature and low quality; and 3) What major conclusion, as identified in the summary for policy makers could not have been made without use of that reference. If you decline this challenge, you show your entire argument to be based on innuendo rather than analysis. At its best, it would amount to an argument from reverse authority - ie, the literature is classified as not authoritative (ie, grey) and therefore is automatically rejected on that basis alone. Personally, I am going to enjoy your attempts to explain why: Agassiz, L., 1837: Discours d’ouverture sur l’ancienne extension des glaciers. Société Helvétique des Sciences Naturelles, Neufchâtel. and Lorenz, E.N., 1967: On the Nature and Theory of the General Circulation of the Atmosphere. Publication No. 218, World Meteorological Association, Geneva, 161 pp. ought to be considered to be of poor quality and not worth referencing, even though they are undoubtedly grey literature. Finally, please note that if you cannot show for any reference point (3) above, you have not shown Pachauri's that the conclusions of the IPCC reports are based on the peer reviewed literature to be false.
  3. Tom @ 74, Your point that lead authors are part of a team is well made. I reviewed the CV of the author that Krisbaum linked to. Apparently he had received a MS in Geology shortly before the 1994 IPCC report and received his PhD in 2004 after he was a lead author. He remains an expert in the field. I noticed in his list of publications an unusually large number of book chapters. From this I conclude that the author is an exceptional writer and summarizer of others work, just what you need for a lead author of a summary report. It is typical of fake skeptics to make mountains of nits that are irrelevant to the point. In any case, if you have to go back to 1994 to find an author that you think might have been inappropriate for an unpaid position writing a report that was not very important at the time you are looking very hard to be disappointed. When did you last cite the 1994 report? Where I live it is 2012. This shows that all of the writers for the third and fourth IPCC reports were qualified.
  4. I think it's simple question time: What does the IPCC's use of grey literature mean for you, krisbaum?
  5. Moderator, is it against the comments policy to point out evidence of motivated reasoning on Krisbaum's part?
    It [an IPCC report] is used to decide the fate of trillions of dollars of investment through carbon taxes or emissions trading schemes.
    It appears Krisbaum is concerned about the cost of mitigating AGW, and is really making an argument from consequences . If so, perhaps he should be directed to The economic impacts of carbon pricing thread.
    Response: [DB] It is always welcome to suggest more appropriate threads for portions of discussions, if applicable. The one you suggest would indeed be a valid thread to continue that portion of the discussion.
  6. Tom@77; ' Your attack on the IPCC's integrity is based on the fact that the IPCC uses grey literature, and indeed it says it does.' Tom, I have repeated the point a few times now. Pachauri and the IPCC boast that their reports are only based on Peer Reviewed literature. If the reports are not baed on Peer Reviewed literature, it should be made completely clear. eg. “People can have confidence in the IPCC’s conclusions…Given that it is all on the basis of peer-reviewed literature.” – Rajendra Pachauri, IPCC chairman, June 2008 “The IPCC doesn’t do any research itself. We only develop our assessments on the basis of peer-reviewed literature.” – Rajendra Pachauri, IPCC chairman, June 2007 “This is based on peer-reviewed literature. That’s the manner in which the IPCC functions. We don’t pick up a newspaper article and, based on that, come up with our findings.” – Rajendra Pachauri, IPCC chairman, June 2008
    Response: [DB] You even quote Tom Curtis who points out the IPCC says it uses grey literature. Without further equivocation, please show via link to credible source where the IPCC states it only uses peer-reviewed literature. It is patently, completely clear your issue is with Pachauri, not the IPCC.
  7. krisbaum, where did Michael say "leader of their field"? He said "lead writer" or "lead author." You also say that the IPCC reports are not based on peer-reviewed literature. That is not true. They are based on both peer-reviewed literature and grey literature. The quantities of both categories have been amply given. If a building rests on a foundation of 4000 blocks of granite and five blocks of sandstone, is it fair to say that the building does not rest on granite? The people on this website find the IPCC to be an excellent resource, because the IPCC has gathered and summarized published climate research. Why wouldn't the IPCC be a good resource? It's a huge, multifaceted project. You use the nitpick of Pachauri to cast doubt on the whole enterprise. It's like me saying, "Well Anthony Watts' new study did not take time-of-day into account. Therefore, all 'skeptics' should be ignored (because they're frauds, man!)."
  8. Krisbaum @81, I have challenged you to show an example of inappropriate use of non-peer reviewed literature in the IPCC, and you have declined to take up that challenge. The challenge included a specific element of showing were major conclusions of the IPCC were derived from grey literature of any sort (not just the non-peer reviewed grey literature). Yes, it is true that the IPCC uses grey literature. Some of that literature may even be considered inappropriate. For example, the IPCC AR4 WG1, Chapter 1 cites Gwynne, P., 1975: The cooling world. Newsweek, April 28, 64. On its face, citing an article in Newsweek is a classic example of use of inappropriate sources. However, consider the context in which it was used:
    "Not all theories or early results are verified by later analysis. In the mid-1970s, several articles about possible global cooling appeared in the popular press, primarily motivated by analyses indicating that Northern Hemisphere (NH) temperatures had decreased during the previous three decades (e.g., Gwynne, 1975)."
    So, an article from a popular news magazine was cited to demonstrate that articles about possible global cooling have appeared in the popular press. In history, that is called consulting primary sources, and is considered far preferable to consulting secondary sources, eg, a peer reviewed article about popular publications on climate change in the mid 1970s. Despite this being excellent academic practice, you want to cite this as an example of poor academic practice by the IPCC. What is more, you want to do so purely on the basis of the presence of the citation with absolutely no examination of the actual use made of the citation. Another example of grey literature in Chap 1 of WG1 is Hawking, S., 1988: A Brief History of Time. Bantam Press, New York, 224 pp. Technically, A Brief History of Time is not grey literature because it was published by a commercial publishing house. That your primary source classifies it as grey literature simply shows them to be incompetent at their self appointed task. But I will grant that it is a popular book, and probably not peer reviewed. So how was it used?
    ". It is not the belief or opinion of the scientists that is important, but rather the results of this testing. Indeed, when Albert Einstein was informed of the publication of a book entitled 100 Authors Against Einstein, he is said to have remarked, ‘If I were wrong, then one would have been enough!’ (Hawking, 1988); however, that one opposing scientist would have needed proof in the form of testable results."
    Well I'm just devastated. Clearly this hugely inappropriate use of an Einstein quotation completely overthrows any basis of confidence in IPCC reports! /sarc I say end sarc, but my sarcastic comments in fact represent your actual case. Chapter 1 of WG1 was given a grade of B for the use of non-peer reviewed sources from your favourite source. Now, first it should be noted that the majority of "grey literature" cited in the IPCC is extensively reviewed by peers of the authors before publication - as for example with white papers, or reports from scientific organizations, or indeed IPCC reports themselves. They are not grey literature because they are or are not peer-reviewed, but because of their method of publication. Second, it should be noted that your favourite sources have listed as grey literature many items which, while not peer reviewed, are in fact not grey literature. An example, the article by Agassiz, was given in my prior post. But the fact that it was not peer reviewed before publication no more makes Agassiz ground breaking work inferior science than the same lack of peer review makes Einstein's seminal papers on relativity inferior science. So, bearing in mind those two fatal flaws in their classification system, the appropriate question is how many poor quality sources have been used by the IPCC. In chapter 1 of WG1, so far as I have been able to determine - just two. The two quoted above. And as demonstrated, their use was entirely appropriate. It becomes blatantly clear that your entire argument depends on your not examining details. As an argument based on not examining details is always a con job, I would recommend that in future you only present detailed examples which are shown to be sources of poor quality (not just grey literature, and not just non-peer reviewed, but of a genuinely questionable quality) and which you show significant conclusions to depend upon, ie, the significant conclusion cannot be drawn from other sources of high quality also cited by the IPCC. If you are unwilling to take up that challenge, you show thereby that when examined in detail, there is no basis to question the IPCC's use of sources. You will also show by your failure that your entire case consists in sloganeering. Finally, you keep on coming back to quotes by Pachauri as if they somehow prove the IPCC has said it does not use grey literature despite the direct statement by the IPCC documents that they do. However, I'm game. If you want to prove Pachauri wrong, all you need to do is prove that a questionable source is relied upon by the IPCC for a main conclusion. After all, Pachauri does not say that the IPCC never cites grey literature. He says that they do not rely on non-peer reviewed literature for their findings. And that is only the case if the IPCC has a major finding which they would not have reached without the citation of dubious quality. Put simply, showing that the IPCC cited Newsweek did not prove Pachauri wrong, for no substantive conclusion about climate science was reached from that citation. PS: Given your thesis, in future I will not accept any citation by you of grey literature as evidence. You may find that embarrassing as the only evidence you have cited has all been from grey literature; but better to be embarrassed than hypocritical as you are currently being.
  9. I agree with Tom here. To allow Krisbaum to register any point by claiming that Pachauri overstates his claim does not seem fair to me. I haven't seen any evidence presented that Pachauri's claims, quoted by Krisbaum or anyone else in this thread, are overstated. I.e., I agree with Tom that it can be entirely consistent to draw conclusions based only on peer reviewed literature while still citing other literature. In the absence of anyone being able to give concrete contrary examples, this is the case for Pachauri and the IPCC. It certainly is fair to state that Krisbaum's claims are overstated, and embarrassingly so. There is nothing to his claims. But it is not clear to me that Krisbaum is being demonstrably hypocritical. I don't think he is claiming that any statement should only be based on peer reviewed literature. To hold someone else to a higher standard than held for oneself is certainly likely to be unreasonable, but it need not be hypocritical. It may be that in his mind, Krisbaum merely thinks he is holding Pachauri to a self-imposed standard that Krisbaum believes Pachauri/IPCC has failed to live up to. I hope that Krisbaum has the fairness of mind to either demonstrate his claims and/or honestly admit his reasoning is at best misguided. The rest of Tom's above post makes an entirely salient point with pertinent examples, and is what Krisbaum needs to respond to in order to attempt any substantiation of his claims.
  10. Daniel Livingston @84, you may think it is not hypocritical of Krisbaum to use grey literature. It cannot have escaped your notice, however, that his entire argument depends on his pointing to the existence of grey literature without any discussion of the extent, quality or use of that literature. If the mere fact of literature being grey, is in his opinion, sufficient to rule it out as an acceptable source, then he is hypocritical to cite grey literature to establish his case. However, if he publicly and without equivocation states that grey literature can be of the the highest quality, and that the citation of grey literature by the IPCC in no way, by itself detracts from the quality of the IPCC reports, I will certainly withdraw the claim of hypocrisy and consider grey literature he adduces in support of his case. Without such a clear statement, however, I feel the conclusion that he is being hypocritical must stand.
  11. Fair enough reasoning, Tom Curtis @ 85. I see Krisbaum has dug more of a hole for himself than I at first realised. I hope he'll have the openness and honesty to see it.
  12. One can always hope.Since the ball is in Krisbaum's camp, I'll add 2 questions to the challenges posed by others above. Krisbaum, How did you get the impression that aerosols travel only about 10 km from their source? How did you form the opinion that this falsehood was common knowledge?
  13. Krisbaum... Think clearly for a moment. Is Pachauri saying that every single piece of science in the IPCC reports is peer reviewed literature. I don't think so. He's saying that the IPCC reports are "based" on the peer reviewed science. That statement does not exclude other sources. Look, Pachauri is a smart guy. He's not going to make completely unfounded statements, especially in such a high profile position.
  14. Philipe; to expand; it is common knowledge anthropogenic aerosols have a short atmospheric lifetime and therefore a very heterogeneous spatial distribution. 10km is arbitrary, I used it to simplify my statement(s).

    [DB] This image of carbon monoxide aerosols from Asia proves you, and common knowledge, very wrong:

    The source website for that image is The image itself can be found here.

  15. Rob; 'Look, Pachauri is a smarty guy. He's not going to make completely unfounded statements, especially in such a high profile position. ' Please back up this claim with some evidence.
  16. krisbaum... What? Are you looking for test scores to show that he's smart?
  17. Rob - maybe have a dig around the internet yourself, there's plenty of information about grey literature usage in quite important areas of the IPCC's AR4. Maybe start here;
  18. krisbaum... "...aerosols have a short atmospheric lifetime and therefore a very heterogeneous spatial distribution." Please back up this claim with some evidence.
  19. ' Look, Pachauri is a smart guy. He's not going to make completely unfounded statements, especially in such a high profile position. ' Rob, I just showed you how he made unfounded statements, far reaching across the media. Telling the world the reports are only based on peer reviewed literature was misleading.

    [DB] "Telling the world the reports are only based on peer reviewed literature"

    Only? No more making things up. Support this statement with a link to an actual, verifiable quote; this is not an optional exercise.

  20. What kind of a claim do you want Rob? Go pick up a copy of 'Large historical changes of fossil-fuel black carbon aerosols' T. Novakov,1* V. Ramanathan,2 J.E. Hansen,3 T.W. Kirchstetter,1 M. Sato,3 J. E. Sinton,1 J.A. Sathaye1 1Environmental Energy Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
  21. krisbaum... I would suggest you read the rules established by the IPCC on the uses of non-peer reviewed literature. Do you think for some reason Pachauri would be unaware of these policies?
  22. krisbaum @ 95... That's a paper on black carbon. Try again.
  23. krisbaum @89, it is common knowledge that aerosols have a short atmospheric lifetime. It is not common knowledge, because it it not true, that that life time is so short that SO2 emissions in North America and Europe will not impact on SO2 concentrations in Greenland ice. Yet you quoted the made up figure of 10 km in order to rebut the evidence that relative SO2 levels neighbouring the North Atlantic are recorded by Greenland Ice Cores. Without your quotation of that extremely short figure (absurdly short, in fact), you would have had no argument. There is a name for people who make up facts in order to bolster their case. I am not permitted to use it here due to the comments policy.
  24. krisbaum @ 94... Now wait a minute. When I read back on your quotes from Pachauri none of them includes a statement saying that the IPCC uses "only" peer-reviewed literature. Pachauri states that the IPCC reports are "based" on peer reviewed literature. As I tried to point out before those statements do not preclude the use of non-peer reviewed literature. And as I've pointed out there are specific IPCC rules for the use of non-peer reviewed literature that Pachauri is certainly aware of. I would suggest that you're getting worked up over a narrow semantical interpretation of Pachauri's words.
  25. DB: i'm pretty sure you just violated your own posting rules by putting up an animated giff without any references or source whatso-ever.. How do i know you didnt just draw that animation? Where's it from? whats it really mean?

    [DB] The source website for that image is The image itself can be found here.

    Please note that posting comments here at SkS is a privilege, not a right. This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive or off-topic posts, accuse others of deception and make personal attacks on other participants here, make things up and continually complain about moderation. We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site.

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